FastAPI Structure Guide (2026 Optimized Edition)

Intent

Use this guide whenever generating code for a FastAPI project, specifically when:

1. Scaffolding a brand new project.
2. Adding a new feature (e.g., "Add an Order module").
3. Refactoring existing code to meet 2026 clean architecture standards.

You must strictly adhere to the Core Principles, Project Structure, Development Workflow, and Coding Rules defined below.

I. Core Principles

Before writing any code, follow these six guiding principles: